The most likely to leave is probably Heater. Fuller will be promoted to DC. There is no way Matthews returns to Marshall as DC. That isn't going to happen. Doc isn't going anywhere. Legg could go but hard to say how likely it is.
One of the announcers yesterday said with Heater being a Michigan guy it wouldn't surprise him if Heater ends up there next season as an asst. coach after taking over a d that was the worst last season to one of the best this season--reducing the points per game allowed by 20.